There's more than enough research out there to show that every business should have a website. One of those reasons is presence or, in other words, so that people/potential customers have a place to find you. With the ease in which it takes to setup a website and, as little capital that is needed, there's not really a good reason to not have one.
Why is this important: Customers need to be able to find you. A website has the information about how to contact you, where your located, what events you'll be attending, etc. While social media can be used to accomplish this goal, that information can get lost in the mix. It should be used, but as one of many tools. i.e. keep your website updated with current information. This lets people know what's happening with the business, where it will be, and then alert them to changes/updates via social media.
What to Remember: No one knows your business better than you. In other words, your online presence is yours and you need to make it look like yours.